The aviation jet fuel that is used in turbine engines is a hydrocarbon typically manufactured from straight-run kerosene. Exemplary jet fuels include commercial jet fuels including Jet A, Jet A-1 and Jet B type fuels and military aircraft jet fuels including JP-1, JP-4, JP-5, JP-6, JP-7, JP-8 and JPTS. The quality of the jet fuel directly effects aviation safety. Particulate matter present in aviation fuels are most frequently products of solid corrosion (e.g., rust and scale buildup), although catalyst fines, salts and other solids may also contribute to the total amount of suspended particulate matter present in the fuel. A determination of the total suspended solids present in the jet fuel is an essential specification in determining the quality of the fuel. The presence of particulate matter in aviation fuel can increase wear and tear on the precision parts in a jet engine, clog fuel equipment and can cause a wide range of mechanical engine malfunctions, such as for example, filter plugging and other operational problems.
To date, the sole quantitative approved method that has been utilized to determine the total suspended solids present in aviation jet fuels is a gravimetric method that includes the filtration of the solids present in the fuel (as described in ASTM D-5452). This method, however, suffers in that the method is time consuming, frequently requiring four hours or more per sample to complete, requires large amounts of aviation fuel to provide sufficient particulate matter for accurate measurement, for example, at least 3 L, preferably at least 4 L, of the aviation fuel, and requires a specialized metallic container, which is expensive, for collection to the fuel samples. Typically, the allowable limit of total suspended solids in aviation fuel is 1.00 mg/L. Prior art gravimetric techniques have been found to have an average error of approximately 0.02 mg/L.
The use of optical analysis techniques to estimate the total suspended solid content as a volume ratio of the suspended solid to the volume of the jet fuel has been previously described. The prior art optical method, however, first determines a volume to volume ratio of solids to fuel, which is then converted to a weight to volume ratio using an arbitrary density value for the suspended solids. This method, in using an arbitrary assumed density for the particulate matter, provides only an approximate value for the total suspended solids, and cannot be considered an accurate quantitative measurement. Generally, prior art methods can have an error of up to 25% or more of the actual total suspended solids value, which is too large to be considered an accurate measurement because the allowable limit of total suspended solids is only 1.00 mg/L. The inaccuracy of the prior art method is due in part because the method relies heavily upon an estimated density of the suspended particulate solids.
Thus, there exists a need to develop a simple and quick method for the accurate determination of weight per unit volume of solids suspended in jet fuel.